1Regexp: ((a|b|\p{Nd}){1,2}|aaa|bbbb){1,2} 2bab: Ok 3aaca: Fail 4aaabbbb: Ok 5a0b: Ok 6aa0aaa: Fail 7b0aaa: Ok 8Regexp: (\d{1,3}\.){3}\d{1,3} 91.2.3.4: Ok 101.22.333.44: Ok 111.2.3: Fail 121..2.3: Fail 13